Site: Nippon Telegraph and Telephone Corporation (NTT)
1-1 Hikarinooka, Yokosuka-shi
Kanagawa 239, Japan

Date Visited: June 5, 1997

WTEC: N. Helm (report author), K. Bhasin, R. DePaula, C. Mahle



NTT is the biggest domestic communications supplier in Japan. Its network covers all Japanese territory including the remote islands. It employs more than 8,500 research and development personnel. R&D expenditures are approximately $2.5 billion annually, or about 5% of total sales.


NTT has fourteen laboratories working on R&D activities that range from basic scientific research to the development of communication system equipment such as a 400 Gbps optical transmission system, exchange system and a Dick Tracy type wrist telephone for personal communications. NTT has announced as a goal to have an optical fiber to every home in Japan by the year 2010. The Satellite Communications System Laboratory belongs to the Wireless Systems Laboratory that is one of the fourteen laboratories and is located within the Yokosuka R&D Center.

In the Satellite Communications Systems Laboratory, NTT is working in three areas in payload technology aiming for the next generation of large multimedia satellites: large diameter reflector, multibeam array networks and high power amplifiers.

The WTEC team was able to tour the satellite test facility, where research engineers were working on large, deployable, lightweight, metallic mesh reflector modules that are intended to be a 10-15 meter reflector if fully assembled. Each four meter module weighs approximately 9 kg. While this excellent antenna technology has not yet been authorized to an operational spacecraft, it has merit, and the technology will be transitioned to the ETS-VIII spacecraft's reflector.

The team also saw development work on two key technology areas for high power, multibeam antenna arrays: a wafer-scale monolithic microwave integrated circuit and an efficient linear power amplifier.

NTT is developing a multimedia interactive satellite communications system that uses terrestrial circuits for user-to-server transmission with satellite circuits operating at 30 Mbps providing the server-to-user link. The satellite circuits use ATM cell based transmissions to realize the highly flexible transmission system. Therefore, NTT has developed a satellite circuit transmission adapter that terminates terrestrial-circuit transmission frames and translates satellite circuit transmission frames with an ATM cell base, and a satellite circuit receive adapter and a satellite circuit receive board that assembles IP packets from ATM cells and transmits them to the user terminal. It has also developed the file transfer protocols that are used for high throughput with a communications satellite. Currently, as part of this multimedia activity, NTT is conducting an experiment with a multimedia interactive satellite communications system for remote lectures and distance education courses with Tokai University.


In the business area, NTT operates the N-STAR satellite. This large GEO satellite operates in 4 frequency bands (S, C, Ku and Ka) and has 5 kinds of communications systems. N-STAR is used for remote island communication and during traffic congestion for spill-over on the terrestrial networks. N-STAR is the first Japanese communications satellite to provide mobile communications.

NTT is not a manufacturer of communications products, so it makes a public announcement to select the co-developing manufacturing counterparts when it starts to develop new equipment or services


Japan, with a large population in a small territory, has (with the help of NTT) built an excellent terrestrial communications infrastructure. The population, especially the corporate user, expects good quality services. Therefore NTT does not use much satellite communications for domestic service. However, it looks as if NTT is going to be given the right to provide services outside of Japan, and its research activities seem to be directed at that market.


NTT is an excellent company with a long tradition of allocating up to 5% of its total sales to its research and development activities. It has an array of excellent laboratories performing R&D in nearly all areas of communications.

As Japanese companies have been the first to combine computing and communications, it is important to note that Japan also is ahead of the United States in understanding the impact that multimedia systems and markets will have on communications. NTT has reorganized one of its three major laboratory groups to be a "Multimedia System Laboratory Group" with a Multimedia Systems Development Center and a Multimedia Networks Laboratory. Only the Media Lab at MIT compares to these R&D activities in this new technology area.

The deregulation of the national and international communications carriers is taking place in Japan, although the final details have not been released. So the long-term position of NTT will change, not necessarily for the worse, as it will then be able to compete in the international marketplace.

Published: December 1998; WTEC Hyper-Librarian